#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<vector>
using namespace std;


//Definition for singly-linked list.
struct ListNode {
	int val;
	ListNode* next;
	ListNode() : val(0), next(nullptr) {}
	ListNode(int x) : val(x), next(nullptr) {}
	ListNode(int x, ListNode* next) : val(x), next(next) {}
};

class Solution {
public:
	ListNode* removeNthFromEnd(ListNode* head, int n) {
		ListNode* dummyHead = new ListNode(0);
		dummyHead->next = head;
		ListNode* slow = dummyHead;
		ListNode* fast = dummyHead;
		while (n-- && fast != NULL) {
			fast = fast->next;
		}
		fast = fast->next;
		while (fast != NULL) {
			fast = fast->next;
			slow = slow->next;
		}
		slow->next = slow->next->next;
		return dummyHead;
	}
};